udev-util: allocate an event loop of our own for waiting

We can't use the per-thread default one here, as it might already be
running (for example, that's the case in portabled), and our event loops
are not recursive, hence running them a second time is not OK.

src/shared/udev-util.c

@@ -133,7 +133,7 @@ int device_wait_for_initialization(sd_device *device, const char *subsystem, sd_
 
         /* Wait until the device is initialized, so that we can get access to the ID_PATH property */
 
-        r = sd_event_default(&event);
+        r = sd_event_new(&event);
         if (r < 0)
                 return log_error_errno(r, "Failed to get default event: %m");